Darktable and OpenCL - AMD version
Probably you're in the same situation as I: you work with Darktable to process RAW pictures but everything seems slow, despite a capable processor. Export to jpeg sluggish. And still, you have an OpenCL capable videocard, in my case Radeon R7 250 that you want to use. After installing the proprietary drivers, you're still caught with the situation that Darktable is unable to find the proper library (libOpenCL).
The solution seems to be extremely simple: create a symbolic link to the library, somewhere where darktable is capable to find:
ln -s /usr/lib/libOpenCL.so.1 /usr/lib/darktable/plugins/libOpenCL.so.1
This was done on Linux Mint 17.2 (Rebecca) for darktable 1.4 and (almost) the latest AMD Drivers.